Orthodontic biassing device with screw disengagement preventing means

ABSTRACT

Orthodontic biassing devices including various means for preventing screw actuators from becoming disengaged from the body member in which it is cooperatively threadably engaged. The disengagement preventing means may include means directly associated with the screws, and/or stabilizing and retaining rod-like members which are slideably engaged with at least one of the body members of the biassing device. Further disclosed is a means for preventing screws of biassing devices from being backed into the body members due to external pressures applied thereto.

This invention relates to orthodontic devices, and more particularly toorthodontic biassing devices. The present invention is directed toimprovements on biassing devices, such as those disclosed in my priorU.S. Pat. Nos. 3,832,778 and 3,921,294, as well as to other types ofbiassing devices.

In biassing devices having a screw-type actuation member, difficultiesmay arise when the screw actuation member is unthreaded to its maximumextent out of a threaded receiving element, or the like. At this point,there is a possibility that the screw will become disengaged and fallout of the remaining elements of the biassing device. This isundesirable and could cause a dangerous condition in the mouth of thepatient.

The main object of the present invention is to provide orthodonticbiassing devices which are screw actuated and which include means forpreventing the screw from becoming disengaged from the remainingelements of the biassing device.

SUMMARY OF THE INVENTION

In accordance with the present invention, orthodontic biassing devicesare provided with means for preventing the actuating screws frombecoming disengaged from the body housings of the device. The retainingmeans may be either elongated members which are slidably retained in atleast one body member, or may be provided on the screw membersthemselves, or even may be provided in the body housing means tocooperate with the screw members and/or the elongated retaining members.

Additionally, the present invention comprises a nested actuating screwarrangement for increasing the adjustment range of the biassing device,and a telescoping retaining means so that the biassing device may beused over a wider range. Still further, in accordance with the presentinvention, means is provided for preventing the threaded members frombacking into the body housing under the reaction pressure of teeth, orthe like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the main portions of a typicalbiassing device in assembled form;

FIG. 2 is a cross-sectional view of the arrangement of FIG. 1 takenalong the line 2--2 in FIG. 1;

FIG. 3 is a sectional view of a typical retaining member for use in thepresent invention;

FIG. 4 is a partial sectional view of a modified form of the retainingmember of FIG. 3;

FIG. 5 illustrates another type of retaining member for use in thepresent invention;

FIG. 6 illustrates still another embodiment of a retaining device foruse in the present invention;

FIG. 7 illustrates a further retaining device for use in the presentinvention;

FIG. 8 illustrates a modified arrangement of a biassing device accordingto the present invention;

FIG. 9 illustrates a still further modified arrangement of the biassingdevice of the present invention;

FIG. 10 illustrates still another embodiment of the present invention;

FIG. 11 illustrates a further embodiment of the present invention havinga novel screw actuation member;

FIG. 12 illustrates an embodiment of the present invention applied to adifferent type of biassing device;

FIG. 13 illustrates a modified biassing device similar to that of FIG.12 but utilizing a novel screw of the present invention;

FIG. 14 illustrates a still further embodiment of the present invention,similar to that of FIG. 1, but having rectangular end members and tworetaining members;

FIG. 15 illustrates another embodiment of the present inventioncombining concepts of FIGS. 12 and 13;

FIG. 16 illustrates yet another embodiment of the present invention;

FIG. 17 illustrates another embodiment of the present invention;

FIG. 18 illustrates a further embodiment of the present invention;

FIGS. 19 and 20 illustrate a still further implementation of the presentinvention;

FIGS. 21 and 22 illustrate two embodiments of telescoping stabilizingand retaining devices according to the present invention;

FIG. 23 illustrates a still further embodiment of the present invention;

FIG. 24 illustrates yet another embodiment of the present invention;

FIGS. 25 and 26 illustrate a retaining member in accordance with thepresent invention;

FIG. 27 illustrates a double screw arrangement for use in the presentinvention; and

FIGS. 28 and 29 illustrate further double screw arrangements accordingto the present invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

The orthodontic devices of the present invention may be used similarlyto those described in my prior U.S. Pat. Nos. 3,832,778 and 3,921,294,the contents of which are incorporated herein by reference. The presentinvention may also be used with other types of orthodontic biassingdevices which do not specifically embody the inventive concepts of mysaid prior patents. Generally, the orthodontic devices of the presentinvention are adapted to be either directly connected to a tooth viawire members extending from the orthodontic devices, or to be embeddedin acrylic devices which engage respective teeth, the orthodonticdevices being utilized to vary the distance between the acrylic membersand to thus spread apart teeth. The orthodontic expansion devicesdescribed herein can be easily adapted to operate as contraction deviceswithin the scope of the present invention, as disclosed and claimedherein. Still further, the orthodontic devices of the present inventionmay be embedded in an acrylic device and be used to apply pressure toteeth relative to the acrylic device.

Referring to FIGS. 1 and 2, an expansion type orthodontic deviceincludes two body members 11,12, each of which has an internal threadwhich respectively meshes with oppositely threaded screw portions 13,14of an expansion screw 10. Positioned between the two screw portions13,14 is a non-threaded spindle engaging portion 15 which is providedwith radial holes 16 adapted to be engaged by a special tool or simplyan elongated pin which may fit into the holes 16 so as to rotate thespindle. Rotation of the portion 15, which causes relative rotationbetween the screw portions 13,14 and the body members 11,12, eitherspreads the body members 11,12 apart or pulls them toward each other,depending upon the direction of rotation of the spindle engaging portion15. In FIG. 1, the shell member 17 and cover 23 are shown only on theleft-hand body member 11. A similar shell and cover may be provided forbody member 12, for example as illustrated in my U.S. Pat. No.3,921,294. The wire 19 attached to the shell 17 is attached to teeth bymeans of, for example, bands, or the like.

Each of the body members 11,12 has a bore 30,31 formed therein, each ofwhich are in communication with respective smaller bores 32,33. Astablizing rod-like member 34 passes through the smaller bores 32,33 andhas enlarged end portions 35,36 which are slideable within the largerbores 30,31, respectively, but which do not pass through the smallerbores 32,33. As the screw 10 is unscrewed from the body members 11,12,and reaches toward the end of its travel, the enlarged portions 35,36 ofrod member 34 will abut against the end walls of bores 30,31 adjacentbores 32,33, respectively, to prevent further spreading apart of thebody members 11,12. Thus, the bar 34, with its enlarged ends 35,36,stabilizes the end body members 11,12 to prevent wobbling, and furtherlimits the travel of the end body members 11,12 to prevent the screw 10from becoming disengaged from end members 11,12.

As illustrated in FIG. 14, the end members 11,12 may be rectangular inshape and the expansion device may include two or more retaining andstabilizing rods 34, as desired. It should be clear that the end membersmay take any desired shape and that the rods 34 may also take anydesired shape, such as rectangular, round, oval, etc. Further, the rods34 may be hollow or solid, as will become apparent from the following.

FIG. 3 illustrates a hollow rod 40 having flanged ends 41 to act as thestop members as described in connection with FIGS. 1 and 2.

FIG. 4 illustrates a partial embodiment of a tubular or hollow rod 40having gently flared ends 42 which may be formed, for example, byramming a tapered member in the end of a tube.

FIG. 5 illustrates a rod 43, which may be solid or hollow, and having anupset head 44 at the left end thereof and a brazed or welded flangewasher 45 at the right end thereof.

FIG. 6 illustrates a further rod 46 according to the present inventionhaving ends drawn into a restricting ball 47, for example by arcwelding. In FIG. 6, at the right end thereof, the portion 48 which isdrawn into the ball 47 is shown in phantom lines.

FIG. 7 illustrates a rod 49 which has crimped ends 50,51. The ends 50and 51 are shown perpendicular to each other so as to clearly illustratethe crimps. The crimped ends 50,51 may be formed by conventional means,such as hammering, squeezing, or the like.

FIG. 8 partially illustrates a further embodiment of the presentinvention wherein a body member 11' has a screw 13, which is part of ascrew 10, threaded therein and a stabilizing rod 52 slideably mounted ina bore 53 in the end member 11'. The end member 11' further has aslotted portion 54 in communication with the bore 53 through which a pin55 attached to the rod 52 passes. FIG. 8 illustrates only the left bodymember 11'. The right body member may be similar to the left body memberor may be different, as desired. As the body members are expanded awayfrom each other, the pin 55 will eventually abut against the wall 56 ofslot 54, thereby preventing further movement of the body member 11'relative to the screw 13, to stabilize the device and to preventdisengagement of the screw 13 from the body member 11'.

FIG. 9 partially illustrates a further embodiment of the presentinvention wherein a body member 11' has a groove 57 formed therein, astabilizing bar 58 being slideably mounted in the grove. The stabilizingbar 58 has a "pinched up" end 59 which abuts against the end wall 60 ofthe groove 57 to limit movement of the body member 11" relative to thebar 58.

FIG. 10 partially illustrates a further embodiment of the inventionsimilar to that of FIG. 9 except that the groove 64 is generallyrectangular in cross-section and a generally rectangular rod 61 isslideably mounted therein. The rod 61 has an upstanding portion 62 whichabuts against an end surface 63 of the groove 64 to limit movement ofthe end member relative to the rod 61.

FIG. 11 illustrates another embodiment of the invention similar to thatof FIGS. 1 and 2, but wherein the screw members 13',14', havenon-threaded end portions 70,71 which are of reduced diameter relativeto the maximum external diameter of the screws. As the screw device 10'is unthreaded from the end members 11,12 to its maximum extent, the endportions 70 and 71 will remain in the threaded bores 72,73,respectively, thereby preventing the screw device 10' from becomingdisengaged from the end members 11,12. The modified screw device 10' canbe used by itself in the end members 11,12, or may be used inconjunction with rod member 34 having enlarged ends 35,36, asillustrated in FIG. 11, to provide still further stability andprotection against disengagement of the screw device 10' from the endmembers 11,12. As should also be apparent, more than one rod member 34may be used in conjunction with modified screw device 10'.

FIG. 12 illustrates another type of orthodontic device with which thepresent invention is useful. A body member 80 is connectable to, forexample, a tooth, by means of wires, bands, or the like, or is embeddedin an acrylic appliance. The body member 80 has first and second bores81,82 formed therein, through which a bar-type member 83 is slideable.The bar member 83 has a pushing member 84 at the end thereof forapplying an orthodontic force. At the opposite end of bar 83 is anenlarged portion 85 which passes through first bore 81, but does notpass through second bore 82. Thus, the enlarged portion 85 will limitthe movement of the bar 83 relative to the body member 80. By turningthe screw 86, which is threadably engaged in a threaded bore of the body80, the bar 83 and its pushing member 84 are moved to the right relativeto the body member 80 as seen in FIG. 12. The enlarged end portion onthe rod 83 prevents disengagement of the screw 86 from the body member80.

FIG. 13 illustrates a further embodiment of the present inventionwherein the pushing member 84 is connected to a threaded member 87 whichis threadably engaged in a threaded bore 88 of a body member 89. Thescrew 87 has a reduced diameter non-threaded portion 90 at the endthereof. As the screw is unthreaded from the body member 89 to itsmaximum extent, the reduced diameter portion 90 will remain in thethreaded bore 88 to prevent disengagement of the screw 87 and pushingmember 84 from the body member 89. A rotatable joint may be providedbetween member 84 and screw portion 87 so that the screw portion 87 mayrotate relative to the member 84.

As should be apparent, the concepts of FIGS. 12 and 13 could be combinedby providing a reduced diameter non-threaded portion 91 at the left endof the screw 86', as shown in FIG. 15. Thus, the embodiment of FIGS.12,13 and 15 provide not only stability of the pushing member 84, butalso prevent disengagement of the pushing member 84 and its associatedrod, either threaded or unthreaded from the body member 80,89. A coilspring 101 is optionally provided as shown in FIG. 15 in order to biaspushing member 84 against screw 86' to facilitate insertion of thedevice into the mouth of a patient.

While it is preferable to have the stabilizing and disengagementpreventing rod 34 freely slideable in both end body members 11,12 asshown in FIGS. 1 and 2, it is possible to provide one or morestabilizing rods which are fixed in one of the end body members, andwhich is slideable in the other of the body members, the slideable endhaving an enlarged end portion as shown in FIGS. 1 and 2. Such amodified form of the invention is shown by way of example in FIG. 16.

Referring to FIG. 16, the body member 11 and the screw device 10 aresimilar to the corresponding elements in FIGS. 1 and 2, andcorresponding reference numerals are used. The body member 92 at theright side of the embodiment of FIG. 16 has a stabilizing anddisengagement prevention rod 95 fixed thereto. The free end of the bar95 is slideable in the bores 30,32 of body member 11, said free end ofthe bar 95 being roughened or otherwise formed at 96 so as not to passthrough the smaller diameter bore 32. It should be clear, however, thatthe free end 96 of bar 95 may be otherwise formed such as, for example,shown in the other figures of the drawings. As seen in FIG. 16, when thescrew device 10 is fully threaded in both of the body members 11,92, dueto the fact that the bar 95 is fixedly mounted in one of the bodymembers 92, the free end 96 will extend outwardly of the body member 11.In some instances, an obstruction in the mouth of a patient couldprevent use of the embodiment of FIG. 16 wherein the bar member 95extends outwardly (that is, to the left) of the body member 11 as seenin FIG. 16. This is due to the fact that relative movement between thebar 95 and the end body member 11 will be twice the relative movementbetween the screw portion 13 and the body member 11. This is due to thefact that the bar 95 is fixed at one end to body member 92. In order toprevent the bar 95 from projecting outwardly of the body member 11, ascrew 10 having a smaller length must be used.

As should be apparent from the above, the embodiment of the presentinvention wherein both ends of the bar 34, for example as shown in FIG.2, are freely slidable in the respective body members 11,12, has theadvantage that full travel of the body members 11,12 relative to thescrew member 10 can be provided without having either end of the bar 34project outwardly of the outer extreme ends of body members 11,12. This"floating" movement of the retaining and stabilizing bar 34 relative tothe body members 11,12 is therefore advantageous.

FIG. 17 illustrates another embodiment of the invention comprising bodymembers 102,103 having small diameter threaded bores 104,105,respectively, which threadably engage oppositely threaded screw portions106,107, respectively, of an expansion screw 108. Threaded bores 104,105are in communication with larger diameter bores 109,110, respectively,of body members 102,103. The ends of the screw portions 106,107 arecrimped or otherwise deformed or enlarged so that they freely passthrough bores 109,110 but do not pass through threaded bores 104,105.Body members 102,103 are attached to teeth by means of wires, or thelike, in the same manner as the body members of FIGS. 1 and 2. As thethreaded screw member 108 is unthreaded from body members 102,103, whenthe screw portions 106,107 reach the end of their engagement withthreaded bores 104,105, the crimped end portions 111,112 will not passthrough threaded bores 104,105, thus limiting movement of the threadedscrew 108 relative to the body members 102, 103. This prevents the screwmember 108 from becoming disengaged from the body members and fallinginto the mouth. Stabilizing rods, such as rod 34 or the like could beused in conjunction with the expansion screw 108 shown in FIG. 17, asshould be apparent.

It should be clear that the embodiment of FIG. 13 could be modified toprovide an enlarged end on screw 87 in place of the reduced diameterportion, and to provide an enlarged bore in communication with a smallerthreaded bore as shown, for example in FIG. 17, to limit unthreading ofscrew 87 from body member 89.

FIG. 18 illustrates a further embodiment of the invention wherein astabilizing and retaining rod 115 is slideably mounted in a bore 116 ofa body member 117. The rod 115 has an elongated depression 118 thereinand the body member 117 has a pin or set screw 119 therein so as tointrude into the void presented by the depression 118. As the rod 115moves out of the body member 117 upon actuation of the screw member 10,the pin or set screw 119 will abut against the end wall 120 ofdepression 118 so as to limit the travel of the rod 115 relative to thebody member 117, thereby preventing screw member 10 from becomingdisengaged from body member 117. The right-hand portion of the deviceshown in FIG. 18 may be identical to the illustrated left end portion,or may be modified as, for example, one of the previously describedarrangements.

FIG. 19 illustrates a modified form of the arrangement shown in FIG. 11.In the embodiment of FIG. 19, respective bores 72,73 of body members11,12 have enlarged or unthreaded mouth portions 74,75. As the expansionscrew 10 is unthreaded from the body members 11,12, when the screwportions 13,14 reach the unthreaded or enlarged mouth portion 74,75,further expansion of body members 11,12 ceases. The unthreaded portions74,75 act as retainers to prevent the expansion screw 10 from becomingdisengaged from the body members 11,12. The enlarged openings 74,75 maybe used in conjunction with one or more stabilizing rods or bars 34, asshown in FIG. 19 or in any of the other figures, or may be used withoutsuch stabilizing rods or bars, as should be apparent.

FIG. 20 is a modified form of the invention using the conceptillustrated in FIG. 19. FIG. 20, which is similar to the arrangement ofFIG. 13, utilizes an enlarged, non-threaded portion 93 at the opening ormouth of the threaded bore 88 so that as the screw member 87 isunthreaded from the body member 89, the displacement between the screwmember 87 and the body member 89 ceases when the screw member reachesthe unthreaded portion 93, thereby preventing the screw member frombecoming disengaged from the body member 89. Since the device of FIG. 20operates as an expansion device, and there is always pressure againstmember 84 tending to push the threaded member 87 back into the threadedbore 88 of the body member 89, there is very little danger that thethreaded member 87 will become disengaged from the body member 89. Itshould be clear that the arrangement of FIG. 20 may be utilized inarrangements such as those shown in FIGS. 12 and 15. Also, stabilizingbars, or the like, could be used with this embodiment.

With respect to FIGS. 19 and 20, it should be clear that the precisedimensions and arrangements of the openings 74,75 and 93 may be variedwithin rather wide limits. The length of the opening in the axialdirection of the threaded bores may also be varied. Still further, theportions 74,75 and 93 need not be unthreaded, but may be dimensioned orconfigured such that the respective threaded members will not moverelative to the respective body members when they are turned in theportions 74,75 and 93.

FIGS. 21 and 22 illustrate telescoping retaining and stabilizing barsfor use in the present invention. Telescoping retaining and stabilizingbars are particularly useful in, for example, the embodiment of FIG. 16wherein one end of the bar is fixed to a body member. The arrangementsof FIGS. 21 and 22 may have one end fixed in a body member, such asshown in FIG. 16.

Referring to FIG. 21, the telescoping member comprises an outer tubularmember 100 having a slot 101 along the axial direction thereof. The slotis closed at the remote end 102 of the outer tubular member 100.Slideably mounted within the outer tubular member 100 is an innerrod-like member 103 which may be solid or tubular, and which has anenlarged portion 104 at the end thereof. The enlarged portion may becrimped, deformed, roughened or any of the other particularconfigurations illustrated in the drawings. The outer tubular member 100may have a similar enlarged end portion 105, or may be straight forembedding same in a body member, such as body member 14 of FIG. 16. Theinner rod 103 has a pin or the like protruding therefrom which engagesin the slot 101. As can be seen from FIG. 21, when the inner rod 103 iswithdrawn to its maximum extent from the outer tubular member 101, thepin 104 will abut the end portion 102 of the outer tubular member 100 toprevent further displacement between the inner rod and outer tubularmember.

FIG. 22 shows a modified arrangement wherein an outer tubular member 110has a pin 111 mounted at the end thereof and which extends to theinterior of the outer tubular member 110. Slideably mounted within theouter tubular member 110 is an inner rod, or the like 113 which has alongitudinal groove 114 formed therein. As the inner rod 113 iswithdrawn from the outer tubular member 110, the pin 111 will eventuallyabut against the end portion 115 of the inner rod 113 to prevent furtherdisplacement of the inner rod 113 relative to the outer tubular member110.

The embodiments of FIGS. 21 and 22 are exemplary and it should be clearthat various modifications and alterations can be made to still providetelescoping guide and retaining bars for the biassing devices of thepresent invention.

FIG. 23 illustrates a further embodiment of the present inventionutilizing a nesting expansion screw arrangement. This provides increasedexpansion lengths while reducing the intervals between changing ofexpansion screws. As shown in FIG. 23, the expansion screw 120 comprisesinner screw members 121,122 which are oppositely threaded. Theoppositely threaded screws 121,122 have respective abutment members123,124 at the ends thereof, the functions of which will become apparentfrom the following discussion. The expansion screw 120 further comprisesouter screw members 125,126 which respectively threadably engage innerscrews 121,122 at the threaded portions 227,228 thereof. The outersurfaces of outer screws 125,126 are oppositely threaded with respect toeach other. The outer screws 125,126 have abutment members 127,128,respectively, at the ends thereof. The outer threads of the outer screws125,126 threadably engage threaded portions 129,130 of respective bodymembers 131,132. The body members 131,132 are only partially shown, itbeing clear that stabilizing and retaining bars, such as those shown inany of the previously described embodiments, could be used inconjunction therewith. In the illustrated embodiment, the threads of thevarious screw members have the same pitch. However, different pitchescould be used for the inner and outer screws, if desired.

In operation, as the spindle engaging portion 133 of the expansion screw120 is rotated by the user, either the inner or outer screws will alsorotate relative to the respective body members 131,132. It is notrelevant whether the inner or outer screws rotate at this time. By wayof explanation, assuming that the inner screws rotate relative to theouter screws, as the inner screw reaches the end of its threadedengagement with the portion 127,128 of the outer screw. The abutmentmembers 123,124, which are slideable within the hollowed out portions134, 135 of the respective outer screws 125,126, will abut against theinner walls 136,137 of the outer screws to prevent further relativerotation between the inner and outer screws. At this time, furtherrotation of the spindle engaging portion 133 will cause the outer screwsto rotate relative to the respective body members. When the outer screwsreach the end of their threaded engagement with the respective bodymembers 131,132, the abutment portions thereof will abut againstrespective inner wall portions 138, 139 of the respective body members131,132. At this point, the spindle engaging portion 133 can no longerbe rotated, and the expansion screw is prevented from becomingdisengaged from the respective body members.

It should be clear that the embodiment of FIG. 23 may be modified. Forexample, the enlarged end portions 123, 124, 127, 128 are shown only byway of example. Other members or means which prevent relative rotationbetween the respective screws and between the outer screw and the bodymember may be used, or the screw ends could be peened over. Also, it ispossible that when the spindle engaging portion 133 is initiallyrotated, the outer screw will rotate relative to the body member in thefirst instance, and then the inner screw will rotate relative to theouter screw. In this mode of operation, the desired result is stillachieved in that disengagement of the expansion screw 120 from the bodymembers 131,132 is prevented, while providing a full range of adjustmentof the biassing device. As mentioned above, the body members 131,132 areonly partially shown--they clearly may take any desired form, such asround, rectangular, oval, or the like, and are non-rotatably mounted toteeth or other orthodontic members in a mouth of a patient.

FIG. 24 illustrates a further means according to the present inventionfor preventing an expansion screw from becoming disengaged from the bodymembers to which it is threadably engaged. Referring to FIG. 24, anexpansion screw 150 has left and right screw members 151,152 which areoppositely threaded with respect to each other. Screw member 151 isshorter than member 152 by an amount "x". As the expansion screw 150 isthreaded out from respective body members, such as body members 11,12 ofFIGS. 1 and 2, when the shorter portion 151 becomes threadablydisengaged from body member 11, a portion "x" of screw member 152 willremain threaded in the other body member, for example body member 12.This will prevent the expansion screw 150 from becoming completelydisengaged from the expansion device and falling into the mouth of apatient. When the screw member 151 becomes threadably disengaged fromits body member 11, it will usually become somewhat displaced therefromso that the user will readily discover that the expansion screw 150 hasreached its maximum travel. The length "x" by which the longer screw 152is longer than the screw member 151 may be varied, as suits theparticular requirement. However, a value of "x" of about 2-4 mm issuitable for general application.

During orthodontic treatment, it sometimes becomes desirable to ceasefurther actuation of the expansion screw device and to use it as aholding member in the mouth. However, since the teeth will tend tocollapse back to their original positions, the teeth exert a force onthe expansion device which tends to cause the screws to back into thebody members. This is clearly disadvantageous. It is desired at thispoint to lock the screws relative to the body members to prevent thescrews from backing into the body members due to the pressure of thetendency of the teeth to return to their original positions. FIG. 25illustrates a means according to the present invention for preventingthe back pressure of the teeth from causing the screws to back into therespective body members when it is no longer desired to impart furtherexpansion.

Referring to FIG. 25, a means for preventing back pressure from backingthe screws into the body members comprises an elongated generallyU-shaped member which is adapted to be snapped over a screw to retain itin position relative to the body member. The sleeve 140 of FIG. 25 ispreferably made of a material which permits flexing thereof as the ends141,142 are pressed over an expansion screw and snapped into place onthe expansion screw. The ends 141,142 are flared outwardly to facilitatesnapping the member 140 over an expansion screw. The member 140 may bemade of spring metal, relatively rigid plastic material, or the like.When it is made of plastic material, it must have sufficient strength inits longitudinal direction to prevent the backing in pressure of theteeth from causing the screw to back into the body member. The member140 may have weakened areas 142 at which it may be snapped off to adjustsame to the desired length. Alternatively, the length of the member 140may be varied by snipping same off with a cutting implement, such asscissors, diagonal cutters, or the like. FIG. 26 illustrates a member140 snapped into place over a screw of the expansion device andinterposed between the spindle engaging portion 15 and a body member 11.If desired, to improve reliability, a similar member 140 may beinstalled on the other side of the spindle engaging member 15 and theother body member (not shown). Still further, if desired, the member 140may be made large enough to snap over the spindle engaging member 15 andto span the distance between the body members (such as body members11,12 of FIG. 2) to achieve substantially the same result.

FIG. 27 illustrates a nested screw arrangement comprised of inneroppositely threaded screws 160,161 which are threadably engaged in outeroppositely threaded screws 162,163. The screw of FIG. 27 may be used inplace of the expansion screws of any of the embodiments of the inventionas well as in conventional biassing devices.

FIG. 28 illustrates a further nested screw arrangement similar to thatof FIG. 23, but wherein the abutment portions 123', 124', 127', 128'have their outer surfaces threaded and wherein the correspondingenlarged inner bores of the housing and outer screw have their innersurfaces threaded so as to threadably engage the threaded abutmentmembers 123', 124', 127', 128'. The arrangement of FIG. 28 has theadvantage that the threading of the abutment members and of the innersurfaces of the enlarged bores provides a stronger and more rigidexpansion device. Operation of the device of FIG. 28 is substantiallyidentical with that of FIG. 23.

FIG. 29 illustrates a further nested screw arrangement according to thepresent invention wherein the outer housing 131 has a large bore 145which is internally threaded and a smaller bore 129" which is notthreaded. An abutment surface 18" is formed between the outer bore 145and the inner bore 129". An outer member 125" has an abutment member127" at the end thereof which is also threaded so as to threadablyengage the inner threaded surface of large bore 145. The inner member121" is unthreaded and has a threaded abutment member 123" at the endthereof which threadably engages the threaded inner surface of the largebore 134" of the outer member 125". Outer member 125" has a smaller bore227" at the mouth thereof which defines an abutment surface 136" whichabuttingly engages abutment member 123". The surfaces 227" and 129" actas bearing and support members for the elongated members 121" and 125"respectively. The arrangement of FIG. 29 operates substantiallysimilarly to that of FIG. 23 and a detailed explanation of the operationthereof is not given herein.

In FIGS. 27 and 28, only the left-hand portion of the nested screwarrangement is shown. The right-hand portion, however, is identical withthe left-hand portions except that the various threaded members areoppositely threaded with respect to the left and right-hand members toprovide proper expansion upon turning of the spindle engaging member ofthe nested screw arrangements.

In any of the nested screw arrangements illustrated herein, the outerscrew member may have a finer thread (such as, for example, an 8-64thread) than the inner screw member which may have, for example a 3-48thread. Since the outer screw member will have a finer thread, turningof the spindle engagement member will cause the outer or heavier screwto initially turn to provide the initial expansion force. In orthodonticoperations, the initial expansion force is generally the highest andcreates the most back pressure on the expansion device. Therefore, insome instances it is desired that the outer, heavier screw member rotateinitially to provide this intial force, which effect can be obtained bymaking the outer thread finer than the inner thread. Such an arrangementwherein the threads have different pitch is particularly advantageous ina nested screw arrangement wherein only, for example, the outer screwmember has a stop means thereon for preventing rotating thereof relativeto the body housing when a predetermined engagement position is reached.At this point, since relative rotation between the body housing and theouter screw is prevented, the inner screw will of necessity rotate whenthe spindle engaging member is rotated. In instances where there is nodanger of the expansion screw becoming disengaged from the body member,for example when the degree of expansion is known beforehand, such anarrangement using different pitches for the inner and outer screws andusing a rotating prevention means only on the outer screw member isadvantageous in that it provides a more economical to manufacturedevice. In particular, with respect to the arrangement of FIG. 27, theconcept of providing a finer pitch on the outer screw member and a stopmeans therefor, in combination with a more coarse pitch on the innerscrew member is advantageous. Still further, the inner screw member inthe embodiment of FIG. 27 may be the unequal length screw member of FIG.24, to further prevent disengagement of the expansion screw from therest of the device.

The embodiment of FIG. 17 may, for example, be modified along the linesof the concepts illustrated in FIGS. 28 and 29. A modification along thelines of FIG. 28 would comprise replacing the flattened portion 111,112with enlarged cylindrical abutment members which are externallythreaded, and by threading the internal surfaces of bores 109,110 toengage the threaded abutment portions which replace the portions111,112. A modification of FIG. 17 along the lines of FIG. 29 wouldcomprise replacing the end portions 111,112 with cylindrical abutmentportions having a threaded outer periphery, and by threading the innersurface of enlarged bores 109,110. The remainder of the screw portion106,107 would be unthreaded, as would the inner surfaces of the smallerbores 104,105. The elongated unthreaded portions would thus be supportedin the bearing formed by the unthreaded surfaces of the smaller bores104, 105. The enlarged threaded abutment members at the ends of theelongated unthreaded members would abut against the inner surface of thewall which defines the transition between enlarged opening 109,110 andsmaller openings 104,105, respectively.

The arrangement of FIG. 27 is utilizable in conventional orthodonticbiassing devices, assuming that the threaded bore thereof is ofsufficient size to receive the elongated threaded members 162,163. Whenutilizing the arrangement of FIG. 27 in a conventional biassing device,it is preferable that the inner screw members 160,161 have a finerthread than the outer screw members 162,163. Moreover, it is preferablethat the inner screw members 160,161 have abutment means at the endthereof, similar to abutment means 123 shown in FIG. 23, and that theouter screw members 162,163 have, for example, an enlarged bore 134 andsmaller threaded bore 227 so as to cooperate with the abutment member123. This type of modified arrangement will insure that the inner screwrotate initially (since it has a finer threaded) and when the innerscrew reaches the end of its travel (such as when the abutment member123 abuts the wall 136 of the outer screw member), the outer screws 162,163 will be caused to rotate upon further turning of the spindleengaging member. If desired, the outer screw members 162,163 may be thenmade of unequal length, for example as shown in FIG. 24, to furtherprevent disengagement of the threaded members from the body housings, orthe like.

While the invention has been described above with respect to specificembodiments, it should be clear that various modifications andalterations could be made within the scope of the invention as definedin the appended claims. For example, in any of the embodiments, morethan one stabilizing and retaining rod of the present invention could beused to provide improved stability of the device. Moreover, theparticular design of the end members 11,12, 80,89 can be varied, theparticular designs shown in the drawings being merely exemplary.Moreover, the biassing devices may be used in fixed appliances in themouth, as well as removable. They may be mounted via extension arms(i.e., metal arms) or may be embedded in plastic members. The variousfeatures of the invention may be combined in any combination.

I claim:
 1. An orthodontic biassing device comprising:at least one bodymember having a threaded bore therein; an elongated threaded memberwhich is threadably engaged in said threaded bore of said body member,said elongated threaded member comprising an outer threaded memberthreadably engaged in said at least one body member and having athreaded internal bore therein, and an inner threaded member which isthreadably engaged in said threaded bore of said outer member; and meansadapted to couple said biassing device to at least one tooth forapplying an orthodontic force to at least one tooth.
 2. A biassingdevice according to claim 1 comprising two spaced body members adaptedto engage one or more teeth, each of said body members having a threadedbore therein, said threaded bores being oppositely threaded, and whereinsaid elongated threaded member comprises respective inner and outerthreaded members at the respective ends thereof, each pair of inner andouter threaded members being threadably engaged in respective bodymembers.
 3. A biassing device according to claim 1 wherein saidelongated threaded member comprises means for preventing said innerthreaded member from becoming disengaged from said threaded bore of saidouter member.
 4. A biassing device according to claim 3 wherein saiddisengagement preventing means comprises abutment means on at least oneof said inner and outer threaded members.
 5. A biassing device accordingto claim 4 comprising abutment means at the end portion of said innerthreaded member, said abutment means having a threaded outer periherywhich is threadably engaged with a threaded internal bore of said outerthreaded member.
 6. A biassing device according to claim 3 comprisingmeans for preventing said outer threaded member from becoming threadablydisengaged from said at least one body member.
 7. An orthodonticbiassing device comprising:two body members adapted to engage one ormore teeth and to be spaced from each other, each of said body membershaving a threaded bore therein, said threaded bores being oppositelythreaded; first abutment means on at least one of said body members; anelongated inner threaded member having externally threaded end portionswhich are oppositely threaded; a pair of outer screw members havinginternally threaded bores which are threadably engaged over a respectivethreaded end portion of said elongated inner threaded member, said outerscrew members each having oppositely threaded external threads thereonwhich are respectively threadably engaged in the threaded bores of saidbody members to selectively expand or contract the spacing between saidbody members; and retaining means for selectively and abuttinglyengaging with said first abutment means of at least one of said bodymembers for positively preventing relative movement between saidthreaded members and said body members when the spacing between saidbody members is expanded to a predetermined spacing, thereby preventingdisengagement of said threaded members from said body members.
 8. Abiassing device according to claim 7 wherein said retaining meanscomprises means slideably engaged in said at least one body member forselectively and abuttingly engaging said first abutment means of said atleast one body member.
 9. A biassing device according to claim 8 whereinsaid at least one body member has a further bore therein, said furtherbore having a smaller cross-sectional portion and a largercross-sectional portion in communication with said smallercross-sectional portion, and wherein said retaining means comprises atleast one elongated member slideably received in said further bore, saidat least one elongated member having means at an end portion thereofwhich is passable through said larger cross-sectional portion of saidfurther bore but which is not passable through said smallercross-sectional portion of said further bore.
 10. A biassing deviceaccording to claim 9 wherein said means at the end portion of said atleast one elongated member comprises an enlarged portion.
 11. A biassingdevice according to claim 9 wherein said threaded bore of said at leastone body member extends only partially through said at least one bodymember and communicates with a further bore which has a larger internaldimension than said threaded bore, and said retaining means furthercomprises an enlarged portion at the end portion of said outer screwmembers which engages said further internal bore of said at least onebody member, said enlarged portion being passable through said furtherinternal bore and being non-passable through said threaded bore.
 12. Abiassing device according to claim 11 wherein said further bore has aninternal thread thereon and said enlarged portion is threaded tothreadably engage the threads of said larger bore.
 13. A biassing deviceaccording to claim 7 wherein both of said body members comprise saidfirst abutment means and said retaining means includes means forselectively and abuttingly engaging said first abutment means of both ofsaid body members for restricting relative movement between saidthreaded members and both of said body members so as to prevent saidthreaded members from becoming disengaged from said body members.
 14. Abiassing device according to claim 7 wherein said retaining meanscomprises further abutment means coupled to said outer screw members forabuttingly engaging said first abutment means during unthreading thereoffrom said at least one body member for preventing unthreading of saidouter screw members from said at least one body member.
 15. A biassingdevice according to claim 14 wherein said further abutment meanscomprises an enlarged end portion of said outer screw members.
 16. Abiassing device according to claim 14 wherein said further abutmentmeans comprises an outwardly bulged end portion of said outer screwmembers.
 17. A biassing device according to claim 14 wherein saidthreaded bore of said at least one body member extends only partiallythrough said at least one body member and communicates with a furtherbore which has a larger internal dimension than said threaded bore, andsaid further abutment means comprises an enlarged portion at the endportion of said outer screw members which engages said further internalbore of said at least one body member, said enlarged portion beingpassable through said further internal bore and being non-passablethrough said threaded bore.
 18. A biassing device according to claim 17wherein said further bore has an internal thread thereon and saidenlarged portion of said outer screw member has an external threadthereon which threadably engages the internal thread of said largerbore.
 19. A biassing device according to claim 14 wherein said threadedbore of said at least one body member extends only partially throughsaid at least one body member and communicates with a further bore whichhas a smaller internal dimension than said threaded bore, and saidfurther abutment means comprises an enlarged threaded portion at the endportion of said outer screw member which engages said threaded bore ofsaid at least one body member, said enlarged threaded portion beingpassable through said threaded bore and being non-passable through saidsmaller bore.
 20. A biassing device according to claim 14 wherein saidthreaded bore of said at least one body member extends only partiallythrough said at least one body member and communicates with a furtherbore which has a smaller internal dimension than said threaded bore, andwherein said inner threaded bore of said outer screw member extends onlypartially through said outer screw member and communicates with afurther bore in said outer screw member which has a smaller internaldimension than said threaded bore of said outer screw member, andwherein said inner and outer screw members each comprise furtherabutment means at the ends thereof which threadably engage saidrespective threaded bores so as to threadably pass therethrough, butwhich are not passable through the respective smaller internal dimensionbores of the body member and the outer screw member, respectively.
 21. Abiassing device according to claim 7 wherein said outer screw membercomprises further abutment means, and wherein said first abutment meanscomprises an axially extending portion of said threaded bore at themouth thereof which defines a smaller cross-sectional bore portion andwhich abuttingly engages said further abutment means of said threadedmember when said outer threaded member is unthreaded from said at leastone body member such that said outer threaded member is retained in saidlarger cross-sectional threaded portion of said threaded bore,regardless of relative rotation thereof.
 22. A biassing device accordingto claim 21 wherein said threaded bore of said body members comprise anenlarged cross-sectional portion, and said inner threaded bore of saidouter screw members comprise an enlarged cross-sectional portion, saidinner and outer screw members each comprising further abutment means atthe ends thereof which are passable through the respective enlargedcross-sectional bores, but which are not passable through the respectivesmaller cross-sectional threaded portions of said bores.
 23. A biassingdevice according to claim 22 wherein said enlarged cross-sectional boreportions of said body member and of said outer screw member comprisethreaded enlarged cross-sectional bores, and wherein said furtherabutment means at the ends of said inner and outer screw members arethreaded so as to threadably engage the respective enlargedcross-sectional bores.
 24. A biassing device according to claim 7wherein at least one of said body members has a further bore thereinwhich is laterally offset from said threaded bore; said at least onebody member having said first abutment means; and said retaining meanscomprises at least one elongated member coupled to both of said bodymembers and slideably engaged in said further bore of said at least onebody member and having second abutment means for abuttingly engagingsaid first abutment means for positively preventing said relativemovement between said threaded members and said body members to preventdisengagement of said threaded members from said body members and forpreventing relative rotation of said body members about said threadedmembers.
 25. A biassing device according to claim 24 wherein saidfurther bore has a smaller cross-sectional portion and a largercross-sectional portion in communication with said smallercross-sectional portion, and wherein said elongated member of saidretaining means comprises means having said second abutment means at anend portion thereof, said second abutment means being passable throughsaid larger cross-sectional portion of said further bore but not beingpassable through said smaller cross-sectional portion of said furtherbore.
 26. A biassing device according to claim 25 wherein said secondabutment means at the end portion of said elongated member comprises anoutwardly bulged portion.
 27. A biassing device according to claim 25wherein said second abutment means at the end portion of said elongatedmember comprises extending means extending from a surface of saidelongated member generally perpendicular to the longitudinal directionthereof.
 28. A biasing device according to claim 25 wherein each of saidbody members has said further bore therein, and said elongated member isslideably engaged at least in the smaller cross-sectional portions ofsaid further bores and has second abutment means at both ends thereofwhich are passable through said larger cross-sectional portions of saidfurther bores, but which are not passable through said smallercross-sectional portions of said further bores.
 29. A biassing deviceaccording to claim 25 wherein said elongated member is fixedly connectedto the other of said body members.
 30. A biassing device according toclaim 25 wherein said second abutment means at the end portion of saidelongated member comprises an enlarged portion.
 31. A biassing deviceaccording to claim 24 comprising an elongated slot in said at least onebody member and in communication with a portion of said at least onefurther bore, and wherein said second abutment means comprises anabutment member extending from said elongated member and which isslideable in said slot and which is not passable through the portion ofsaid at least one further bore which is not in communication with saidslot.
 32. A biassing device according to claim 24 wherein said elongatedmember comprises an elongated, axially directed depression in a portionof said elongated member except for the end of said elongated member,and wherein said first abutment means comprises means coupled to said atleast one body member and engageable in said depression for abuttingagainst said end of said elongated member for restricting relativemovement between said elongated member and said at least one bodymember.
 33. A biassing device according to claim 24 wherein said atleast one elongated member comprises a telescoping elongated member. 34.A biassing device according to claim 33 wherein said telescopingelongated member comprises a first elongated member having a hollowportion, and a second elongated member slideably received in said hollowportion of said first elongated member, and means coupled to said firstand second elongated members for preventing said second elongated memberfrom sliding completely out of engagement with said first elongatedmember.
 35. A biassing device according to claim 34 wherein said firstelongated member has an elongated slot therein, and said secondelongated member has a pin-like member protruding therefrom andengageable in said elongated slot, said elongated slot having atermination point which is engageable with said pin-like member toprevent disengagement of said first and second elongated members.
 36. Abiassing device according to claim 34 wherein said second elongatedmember has an axial groove therein which terminates short of the end ofsaid second elongated member, and said first elongated member has apin-like member therein which extends into said hollow portion andengages in said groove, said pin-like member engaging an end wall ofsaid groove proximate the end of said second elongated member to preventdisengagement of said first and second elongated members.
 37. A biassingdevice according to claim 24 wherein said threaded bore of said at leastone body member extends only partially through said at least one bodymember and communicates with a further bore which has a smaller internaldimension than said threaded bore, and said second abutment meanscomprises an outwardly extending portion at the end portion of saidouter screw member which threadably engages said threaded bore of saidat least one body member, said outwardly extending portion beingthreadably passable through said threaded bore and being non-passablethrough said smaller bore.
 38. A biassing device according to claim 24wherein said retaining means further comprises third abutment meanscoupled to said inner threaded member for selectively abutting saidouter screw members for preventing unthreading of said inner threadedmember from said outer threaded members.
 39. A biassing device accordingto claim 38 wherein said third abutment means is at the respective endsof said inner threaded member to prevent complete disengagement of saidinner threaded member from said outer threaded members.
 40. A biassingdevice according to claim 24 wherein said elongated member of saidretaining means comprises an inner elongated member and an outerelongated member, said inner elongated member being slideablelongitudinally within said outer elongated member to form a telescopingretaining means, one of said inner and outer elongated members beingslideably engaged in said further bore of said at least one body member.41. An orthodontic biassing device comprising:a body member, said bodymember having a threaded bore therein and first abutment means; anelongated inner threaded member having an externally threaded endportion; an outer screw member having an internally threaded bore whichis threadably engaged over said threaded end portion of said innerthreaded member, said outer screw member having an external threadthereon which is threadably engaged in said threaded bore of said bodymember; means coupled to said inner threaded member for applying anorthodontic force to at least one tooth; and retaining means forselectively and abuttingly engaging with said first abutment means ofsaid body member for positively preventing relative movement betweensaid threaded members and said body member when said outer screw memberis unthreaded a predetermined amount from said threaded bore of saidbody member, thereby preventing disengagement of at least one of saidthreaded members and force applying means from said body member.
 42. Abiassing device according to claim 41 wherein said retaining meanscomprises means slideably engaged in said body member for selectivelyand abuttingly engaging said first abutment means of said body member.43. A biassing device according to claim 42 wherein said force applyingmeans is coupled to said means slideably engaged in said body member.44. A biassing device according to claim 41 wherein said retaining meanscomprises further abutment means coupled to said outer threaded memberfor abuttingly engaging said first abutment means during unthreadingthereof from said body member for preventing unthreading of said outerthreaded member from said body member.
 45. A biassing device accordingto claim 44 wherein said further abutment means comprises an enlargedend portion of said threaded member.
 46. A biassing device according toclaim 44 wherein said further abutment means comprises an outwardlybulged end portion of said outer threaded member.
 47. A biassing deviceaccording to claim 44 wherein said threaded bore of said body memberextends only partially through said body member and communicates with afurther internal bore which has a larger internal dimension than saidthreaded bore, and said further abutment means comprises an enlargedportion at the end portion of said outer threaded member which engagessaid further internal bore of said body member, said enlarged portionbeing passable through said further internal bore and being non-passablethrough said threaded bore.
 48. A biassing device according to claim 47wherein said further bore has an internal thread thereon and saidenlarged portion has an external thread thereon which threadably engagesthe internal thread of said larger bore.
 49. A biassing device accordingto claim 44 wherein said threaded bore of said body member extends onlypartially through said body member and communicates with a further borewhich has a smaller internal dimension than said threaded bore, and saidfurther abutment means comprises an enlarged threaded portion at the endportion of said elongated threaded member which engages said threadedbore of said body member, said enlarged portion being passable throughsaid threaded bore and being non-passable through said smaller bore. 50.A biassing device according to claim 41 wherein said threaded bore boreof said body member extends only partially through said body member andcommunicates with a further internal bore which has a larger internaldimension than said threaded bore, and said retaining means furthercomprises an outwardly extending portion at the end portion of saidouter threaded member which engages said further internal bore of saidbody member, said outwardly extending portion being passable throughsaid further internal bore and being non-passable through said threadedbore.
 51. A biassing device according to claim 50 wherein said furtherbore has an internal thread thereon and said outwardly extending portionof said outer threaded member has an external thread thereon whichthreadably engages the internal thread of said larger bore.
 52. Abiassing device according to claim 41 wherein said outer threaded membercomprises further abutment means and said first abutment means comprisesan axially extending portion of said threaded bore at the mouth thereofwhich defines a smaller cross-sectional bore portion and whichabuttingly engages said further abutment means of said outer threadedmember when said outer threaded member is unthreaded from said bodymember such that said outer threaded member is retained in said largercross-sectional threaded portion of said threaded bore, regardless ofrelative rotation thereof.
 53. A biassing device according to claim 52wherein said threaded bore of said body member comprises an enlargedcross-sectional portion, and said inner threaded bore of said outerthreaded member comprises an enlarged cross-sectional portion, saidinner and outer threaded members each comprising further abutment meansat the ends thereof which are passable through the respective enlargedcross-sectional bores, but which are not passable through the threadedportions of said bores.
 54. A biassing device according to claim 53wherein said enlarged cross-sectional bore portions of said body memberand of said outer screw member comprise threaded enlargedcross-sectional bores, and wherein said further abutment means at theends of said inner and outer screw members are threaded so as tothreadably engage the respective enlarged cross-sectional bores.
 55. Abiassing device according to claim 41 wherein said threaded bore of saidbody member extends only partially through said body member andcommunicates with a further bore which has a smaller internal dimensionthan said threaded bore, and said retaining means comprises an enlargedthreaded portion at the end portion of said enlongated threaded memberwhich engages said threaded bore of said body member, said enlargedportion being passable through said threaded bore and being abuttinglynon-passable through said smaller bore.
 56. A biassing device accordingto claim 41 wherein said threaded bore of said body member extends onlypartially through said body member and communicates with a further borewhich has a smaller internal dimension than said threaded bore, andwherein said inner threaded bore of said outer threaded member extendsonly partially through said outer threaded member and communicates witha further bore in said outer threaded member which has a smallerinternal dimension than said threaded bore of said outer threadedmember, and wherein said inner and outer threaded members comprisefurther abutment means at the ends thereof which threadably engage saidrespective threaded bores so as to threadably pass therethrough, butwhich are not passable through the respective smaller internal dimensionbores of the body member and the outer threaded member, respectively.57. A biassing device according to claim 41 wherein said body member hasa further bore therein which is laterally offset from said threadedbore; and said retaining means comprises at least one elongated memberslideably engaged in said further bore of said body member and havingsecond abutment means for abuttingly engaging said first abutment meansfor positively preventing said relative movement between said threadedmembers and said body member to prevent disengagement of said threadedmembers and force applying means from said body member and forpreventing relative rotation of said body member about said threadedmembers.
 58. A biassing device according to claim 57 wherein saidfurther bore has a smaller cross-sectional portion and a largercross-sectional portion in communication with said smallercross-sectional portion, and wherein said elongated member of saidretaining means comprises means having said second abutment means at anend portion thereof, said second abutment means being passable throughsaid larger cross-sectional portion of said further bore but not beingpassable through said smaller cross-sectional portion of said furtherbore.
 59. A biassing device according to claim 58 wherein said secondabutment means at the end portion of said elongated member comprises anenlarged portion.
 60. A biassing device according to claim 57 whereinsaid second abutment means at the end portion of said at least oneelongated member comprises an outwardly bulged portion.
 61. A biassingdevice according to claim 57 wherein said second abutment means at theend portion of said at least one elongated member comprises extendingmeans extending from a surface of said elongated member generallyperpendicular to the longitudinal direction thereof.
 62. A biassingdevice according to claim 57 wherein said at least one elongated membercomprises a telescoping elongated member.
 63. A biassing deviceaccording to claim 62 wherein said telescoping elongated membercomprises a first elongated member having a hollow portion, and a secondelongated member slideably received in said hollow portion of said firstelongated member, and means coupled to said first and second elongatedmembers for preventing said second elongated member from slidingcompletely out of engagement with said first elongated member.
 64. Abiassing device according to claim 63 wherein said first elongatedmember has an elongated slot therein, and said second elongated memberhas a pin-like member protruding therefrom and engageable in saidelongated slot, said elongated slot having a termination point which isengageable with said pin-like member to prevent disengagement of saidfirst and second elongated members.
 65. A biassing device according toclaim 63 wherein said second elongated member has an axial grove thereinwhich terminates short of the end of said second elongated member, andsaid first elongated member has a pin-like member therein which extendsinto said hollow portion and engages in said groove, said pin-likemember engaging an end wall of said grove proximate the end of saidsecond elongated member to prevent disengagement of said first andsecond elongated members.
 66. A biassing device according to claim 57wherein said elongated member of said retaining means comprises an innerelongated member and an outer elongated member, said inner elongatedmember being slideable longitudinally within said outer elongated memberto form a telescoping retaining means, one of said inner and outerelongated members being slideably engaged in said further bore of saidbody member.
 67. A biassing device according to claim 41 wherein saidretaining means further comprises third abutment means coupled to saidinner threaded member for selectively abutting said outer threadedmember for preventing unthreading of said inner threaded member fromsaid outer threaded member.
 68. A biassing device according to claim 67wherein said third abutment means is at the end of said inner threadedmember which is inside said outer threaded member to prevent completedisengagement of said inner threaded member from said outer threadedmember.
 69. In an orthodontic biassing device comprising at least onebody member having means for engagement with at least one tooth and atleast one threaded bore therein,a threaded actuator comprising: anelongated outer threaded member threadably engaged in said threaded boreof said body member of said orthodontic biassing device, said outerthreaded member further having a threaded internal bore therein; aninner member which is at least partially threaded and which isthreadably engaged in said threaded internal bore of said outer threadedmember; and abutment means coupled to at least one of said threadedmembers for preventing said inner threaded member from becomingthreadably disengaged from said outer threaded member.
 70. An actuatoraccording to claim 69 wherein said disengagement preventing meanscomprises abutment means at least on said inner threaded member forabutting at least a portion of said outer threaded member.
 71. Anactuator according to claim 70 wherein said abutment means is at an endportion of said inner threaded member, said abutment means having athreaded outer periphery which is threadably engaged in said threadedinternal bore of said outer threaded member.
 72. An actuator accordingto claim 69 further comprising further abutment means coupled to saidouter threaded member for preventing said outer threaded member frombecoming threadably disengaged from the threaded bore of said bodymember of said orthodontic biassing device.
 73. An actuator according toclaim 69 having a pair of said elongated outer threaded members whichare oppositely threaded and wherein said elongated inner member has apair of threaded portions which are respectively threadably engageablein said threaded internal bores of said outer members and which arerespectively oppositely threaded.
 74. An actuator according to claim 73comprising further abutment means coupled to at least one of said bodymember and said outer threaded members for preventing said outerthreaded members from becoming threadably disengaged from the threadedbores of said body member of said orthodontic biassing device.
 75. Anactuator according to claim 73 wherein said outer threaded members areof different length.